Examples of nonvolatile memory devices using a resistance material include a phase change random access memory (PRAM), a resistive RAM (RRAM), a magnetic RAM (MRAM), and the like. A dynamic RAM (DRAM) or a flash memory device stores data using charges, whereas the nonvolatile memory device using the resistance material stores data using a phase change of a phase change material such as a chalcogenide alloy (in the case of a PRAM), a resistance change of a variable resistance material (in the case of an RRAM), a resistance change of a magnetic tunnel junction (MTJ) thin film according to a magnetization state of a ferromagnetic material (in the case of an MRAM), and the like.
More specifically, the phase change material is changed to a crystalline state or an amorphous state as it is cooled after being heated. The phase change material in a crystalline state has a low resistance and the phase change material in an amorphous state has a high resistance. Accordingly, the crystalline state may be defined as set data or “0” data, and the amorphous state may be defined as reset data or “1” data.